Shank Assembly

ABSTRACT

In one aspect of the invention, a pick comprises a carbide bolster disposed intermediate an impact tip and a shank assembly. The impact tip comprises a superhard material bonded to a carbide substrate, and the tip is bonded to the bolster opposing a base of the bolster. The shank assembly comprises a central axis, a first end that protrudes into a cavity formed in the base of the bolster, and also an inducible attachment mechanism disposed proximate the first end. The inducible attachment mechanism is adapted to attach the shank assembly to the carbide bolster and restrict movement of the shank assembly with respect to the carbide bolster. The attachment mechanism may restrict movement of the shank assembly in a direction parallel to the central axis.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 11/844,586 filed on Aug. 24, 2007. U.S. patent application Ser. No. 11/844,586 is a continuation-in-part of U.S. patent application Ser. No. 11/829,761, which was filed on Jul. 27, 2007. U.S. patent application Ser. No. 11/829,761 is a continuation-in-part of U.S. patent application Ser. No. 11/773,271 which was filed on Jul. 3, 2007. U.S. patent application Ser. No. 11/773,271 is a continuation-in-part of U.S. patent application Ser. No. 11/766,903 filed on Jun. 22, 2007. U.S. patent application Ser. No. 11/766,903 is a continuation of U.S. patent application Ser. No. 11/766,865 filed on Jun. 22, 2007. U.S. patent application Ser. No. 11/766,865 is a continuation-in-part of U.S. patent application Ser. No. 11/742,304 which was filed on Apr. 30, 2007. U.S. patent application Ser. No. 11/742,304 is a continuation of U.S. patent application Ser. No. 11/742,261 which was filed on Apr. 30, 2007. U.S. patent application Ser. No. 11/742,261 is a continuation-in-part of U.S. patent application Ser. No. 11/464,008 which was filed on Aug. 11, 2006. U.S. patent application Ser. No. 11/464,008 is a continuation-in-part of U.S. patent application Ser. No. 11/463,998 which was filed on Aug. 11, 2006. U.S. patent application Ser. No. 11/463,998 is a continuation-in-part of U.S. patent application Ser. No. 11/463,990 which was filed on Aug. 11, 2006. U.S. patent application Ser. No. 11/463,990 is a continuation-in-part of U.S. patent application Ser. No. 11/463,975 which was filed on Aug. 11, 2006. U.S. patent application Ser. No. 11/463,975 is a continuation-in-part of U.S. patent application Ser. No. 11/463,962 which was filed on Aug. 11, 2006. U.S. patent application Ser. No. 11/463,962 is a continuation-in-part of U.S. patent application Ser. No. 11/463,953, which was also filed on Aug. 11, 2006. The present application is also a continuation-in-part of U.S. patent application Ser. No. 11/695,672 which was filed on Apr. 3, 2007. U.S. patent application Ser. No. 11/695,672 is a continuation-in-part of U.S. patent application Ser. No. 11/686,831 filed on Mar. 15, 2007. All of these applications are herein incorporated by reference for all that they contain.

BACKGROUND OF THE INVENTION

Formation degradation, such as pavement milling, mining, or excavating, may result in wear on impact resistant picks. Consequently, many efforts have been made to extend the working life of these picks by optimizing the shape of the picks or the materials with which they are made. Examples of such efforts are disclosed in U.S. Pat. No. 4,944,559 to Sionnet et al., U.S. Pat. No. 5,837,071 to Andersson et al., U.S. Pat. No. 5,417,475 to Graham et al., U.S. Pat. No. 6,051,079 to Andersson et al., and U.S. Pat. No. 4,725,098 to Beach, all of which are herein incorporated by reference for all that they contain.

BRIEF SUMMARY OF THE INVENTION

In one aspect of the invention, a pick comprises a carbide bolster disposed intermediate an impact tip and a shank assembly. The impact tip comprises a superhard material bonded to a carbide substrate, and the tip is bonded to the bolster opposing a base of the bolster. The shank assembly comprises a central axis, a first end that protrudes into a cavity formed in the base of the bolster, and also an inducible attachment mechanism disposed proximate the first end. The inducible attachment mechanism is adapted to attach the shank assembly to the carbide bolster and restrict movement of the shank assembly with respect to the carbide bolster. The attachment mechanism may restrict movement of the shank assembly in a direction parallel to the central axis.

The attachment mechanism may be adapted to restrict rotation of the shank assembly about the central axis when the shank assembly is attached to the carbide bolster. In some embodiments the inducible attachment mechanism may also be adapted to inducibly release the shank assembly from attachment with the carbide bolster.

The inducible attachment mechanism may comprise an insertable locking mechanism and also a locking shaft connected to an expanded locking head. The insertable locking mechanism and locking head may be disposed within the cavity of the carbide bolster and the locking shaft may protrude from the cavity into an inner diameter of the shank assembly. The locking shaft may be adapted for translation in a direction parallel to the central axis of the shank assembly.

The attachment mechanism may comprise a wedge disposed within the cavity of the carbide bolster. In some embodiments the wedge may be fixed to the carbide bolster. The first end of the shank assembly may be adapted to expand when the wedge is inserted into the first end.

The first end of the shank assembly may comprise a plurality of prongs. The plurality of prongs may be adapted to interlock with the cavity of the carbide bolster. An internal surface of the cavity of the bolster may comprise outwardly tapered surfaces. A split ring may be disposed in the cavity of the bolster intermediate the first end of the shank assembly and an inner surface of the bolster.

The shank assembly may comprise inner and outer diameters. The shank assembly may comprise a hollow portion within the inner diameter and may also comprise an opening to the hollow portion in a second end of the shank assembly. The shank assembly may comprise a constricted inner diameter proximate the first end. A wedge may be disposed within the inner diameter of the shank assembly. In some embodiments the wedge may comprise a first set of threads that corresponds to a second set of threads disposed on an inner surface of the shank assembly.

In some embodiments the attachment mechanism may comprise a plurality of extendable arms that are each perpendicular to a central axis of the shank assembly. Each of the plurality of extendable arms may be adapted to interlock with the carbide bolster by extending into a recess disposed in the cavity of the carbide bolster. In some embodiments fluid pressure on an expandable bladder disposed within the shank assembly may cause the bladder to expand and thereby extend the plurality of extendable arms away from the central axis. Translation of an activating mechanism in a direction parallel to the central axis may extend the plurality of extendable arms away from the central axis. The activating mechanism may interlock with at least a portion of at least one of the plurality of extendable arms and thereby maintains the extension of the arm away from the central axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional diagram of an embodiment of a milling machine.

FIG. 2 is a cross-sectional diagram of an embodiment of a high-impact resistant pick disposed on a milling drum.

FIG. 3 is a perspective diagram of an embodiment of a wedge.

FIG. 4 is a perspective diagram of an embodiment of a portion of a shank assembly.

FIG. 5 is a cross-sectional diagram of an embodiment of a high-impact resistant pick.

FIG. 6 is a cross-sectional diagram of another embodiment of a pick.

FIG. 7 is a cross-sectional diagram of another embodiment of a pick.

FIG. 8 is a cross-sectional diagram of another embodiment of a pick.

FIG. 9 is an exploded cross-sectional diagram of another embodiment of a pick.

FIG. 10 is an exploded cross-sectional diagram of another embodiment of a pick.

FIG. 11 is a cross-sectional diagram of another embodiment of a pick.

FIG. 12 is a cross-sectional diagram of another embodiment of a pick.

FIG. 13 is a perspective diagram of an embodiment of a split ring.

FIG. 14 is a cross-sectional diagram of another embodiment of a pick.

FIG. 15 is a cross-sectional diagram of another embodiment of a pick.

FIG. 16 is a cross-sectional diagram of another embodiment of a pick.

FIG. 17 is a cross-sectional diagram of another embodiment of a pick.

DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENT

FIG. 1 is a cross-sectional diagram of an embodiment of a plurality of picks 101 attached to a driving mechanism 103, such as a rotating drum connected to the underside of a pavement milling machine 100. The milling machine 100 may be a cold planer used to degrade manmade formations such as a paved surface 104 prior to the placement of a new layer of pavement. Picks 101 may be attached to the driving mechanism bringing the picks 101 into engagement with the formation. A holder 102, which may be a block, an extension in the block or a combination thereof, is attached to the driving mechanism 103, and the pick 101 is inserted into the holder 102. The holder 102 may hold the pick 101 at an angle offset from the direction of rotation, such that the pick 101 engages the pavement at a preferential angle. In addition to milling machines, the pick 101 may be adapted for use in a downhole rotary drill bit, in a horizontal directional drill bit, in trenching machines, in mining machines, and in coal mining machines.

Referring now to FIGS. 2-4, each pick 101 may be designed for high-impact resistance and long life while milling the paved surface 104. The pick 101 comprises a shank assembly 200 comprising first and second ends 201, 202. The first end 201 may be press fit into a cavity 203 in a base 204 of a cemented metal carbide bolster 205. A super hard material 206 is bonded to a cemented metal carbide substrate 207 to form a wear-resistant tip 208, which is then bonded to the bolster 205 opposite the base 204 of the bolster 205 and the first end 201 of the shank assembly 200. The shank assembly 200 may comprise a hard material such as steel, hardened steel, or other materials of similar hardness. The bolster 205 may comprise tungsten, titanium, tantalum, molybdenum, niobium, cobalt and/or combinations thereof. The super hard material 206 may be a material selected from the group consisting of diamond, monocrystalline diamond, polycrystalline diamond, sintered diamond, chemical deposited diamond, physically deposited diamond, natural diamond, infiltrated diamond, layered diamond, thermally stable diamond, silicon-bonded diamond, metal-bonded diamond, silicon carbide, cubic boron nitride, and combinations thereof.

The second end 202 of the shank assembly 200 is disposed within a bore 209 of a holder 102, which may comprise an extension 210, a block 211 attached to the driving mechanism 103, or both. The shank assembly 200 may be held into the holder 102 by a retaining clip 212 adapted to fit in an inset portion of the shank assembly 200. An outer surface of the holder 102 may comprise hard-facing in order to provide better wear protection for the holder 102. The hard-facing may comprise ridges after it is applied, though the ridges may be machined down afterward. The base 204 of the bolster 205 may be in direct contact with an upper face 213 of the holder 102, and may overhang the holder 102 and hard-facing, which may prevent debris from collecting on the upper face 213. The bore 209 of the holder 102 may comprise hard-facing. One method of hard-facing the bore is case-hardening, during which process the bore is enriched with carbon and/or nitrogen and then heat treated, which hardens the bore and provides wear protection although other methods of hard-facing the bore may also be used.

The shank assembly 200 may be work-hardened in order to provide resistance to cracking or stress fractures due to forces exerted on the pick by the paved surface 104 or the holder 102. The shank assembly 200 may be work-hardened by shot-peening the shank, chrome plating the shank, enriching the shank with nitrogen, or other methods of work-hardening. The shank may also be rotatably held into the holder, such that the pick 101 is allowed to rotate within the holder 102. The first end 201 of the shank assembly 200 protrudes into the cavity 203 in the base 204 of the bolster 205 and also comprises an inducible attachment mechanism 214. The inducible attachment mechanism 214 is adapted to attach the shank assembly 200 to the carbide bolster 205 and restrict movement of the shank assembly 200 with respect to the carbide bolster 205. In FIG. 2 the inducible attachment mechanism 214 radially expands at least a portion of the shank assembly 200 outward to engage the cavity 203 of the carbide bolster 205. This engagement may attach the shank assembly 200 to the carbide bolster 205, thereby preventing movement of the shank assembly 200 with respect to the carbide bolster 205. The shank assembly 200 may be prevented by the attachment mechanism 214 from moving in a direction parallel to the central axis 403. In some embodiments the shank assembly 200 may be preventing by the attachment mechanism 214 from rotating about the central axis.

In the present embodiment the attachment mechanism 214 comprises a wedge 300 that is disposed within the cavity 203. FIG. 3 is a perspective diagram of an embodiment of a wedge 300 comprising ridges 301 along a portion of an outside surface 302 of the wedge 300. FIG. 4 is a perspective diagram of an embodiment of the first end 201 of a shark assembly 200. The first end 201 comprises a sat 401 into which the wedge 300 may be inserted. As the shank assembly 200 is inserted into the cavity 203 the wedge 300 is forced into the seat 401 of the first end 201, and thereby an expandable portion 402 of the first end 201 is forced outward, away from the central axis 403 of the shank assembly 200, and into engagement with an internal surface 405 of the carbide bolster 205 in the cavity 203. Although in the present embodiment the expandable portion 402 of the first end 201 comprises a plurality of prongs 404, in some embodiments the expandable portion 402 may extend continuously along a diameter of the shank assembly 200.

In FIG. 2 the internal surface 405 of the cavity 203 comprises an apex 230 an intersection of two outwardly tapered surfaces 215 and the cavity 203 comprises a generally hour-glass shaped geometry. The shank assembly comprises inner and outer diameters 216, 217. A hollow portion 218 of the shank assembly 200 is disposed within the inner diameter 216 along at least part of a length 219 of the shank assembly 200. The shank assembly 200 also comprises an opening 220 to the hollow portion 218. The opening 220 is disposed in the second end 202 of the shank assembly 200. In FIG. 2 the opening is controlled by a one-way check valve 221. A lubricant reservoir 223 is disposed in the hollow portion 218 intermediate the check valve 221 and a piston assembly 222.

The pick 101 may be lubricated by inserting a lubricant into the reservoir 223 through the bore 209 of the holder 102 and through the one-way valve 221. The piston assembly 222 may be disposed within the bore 209 such that as more lubricant is inserted into the bore 209, the piston assembly 222 may compress to allow the lubricant to be inserted. After the lubricant is inserted into the bore 209, the piston assembly 222 may apply pressure on the lubricant, which may force it up around the shank assembly 200 and out of the holder 102. This may allow the pick 101 to rotate more easily and may decrease friction while the pick rotates for better wear protection of areas in contact with the holder 102, such as the base 204 of the bolster 205 and the shank assembly 200.

A weeping seal may be disposed around the shank assembly 200 such that it is in contact with the shank assembly 200, the bolster 205, and the holder 102, which may limit the rate at which the lubricant is expelled from the bore 209. The lubricant may also be provided from the driving mechanism. In embodiments, where the driving mechanism is a drum, the drum may comprise a lubrication reservoir and a port may be formed in the drum which leads to the lubrication reservoir. In some embodiments a spiral groove may be formed in the shank assembly 200 or the bore 209 of the holder 102 to aid in exposing the surfaces or the shank and the holder bore to the lubricant. In some embodiments, the lubricant is added to the bore 209 of the holder 102 prior to securing the shank assembly 200 within the holder 102. In such an embodiment, the insertion of the shank assembly 200 may penetrate the volume of the lubricant forcing a portion of the volume to flow around the shank and also compressing the lubricant within the bore.

Dimensions of the shank assembly 200 and bolster 205 may be important to the function and efficiency of the pick 101. A ratio of a length 219 of the shank assembly 200 to a length 225 of the bolster 205 may be from 1.75:1 to 2.5:1. A ratio of a maximum width of the bolster 205 to the outer diameter 216 of the shank assembly 200 may be from 1.5:1 to 2.5:1. The first end 201 of the shank assembly 200 may be fitted into the cavity 203 of the bolster 205 to a depth of 0.300 to 0.700 inches. The cavity 203 of the bolster 205 may comprise a depth from 0.600 to 1 inch. The shank assembly 200 may or may not extend into the full depth 305 of the bore 203. The shank assembly 200 and bolster 205 may also comprise an interference fit from 0.0005 to 0.005 inches. The bolster may comprise a minimum cross-sectional thickness between the internal surface 405 of the cavity 203 and an outside surface of the bolster 205 of 0.200 inches, preferable at least 0.210 inches. Reducing the volume of the bolster 205 may advantageously reduce the cost of the pick 101.

The cemented metal carbide substrate 207 may comprise a height of 0.090 to 0.250 inches. The super hard material 206 bonded to the substrate 207 may comprise a substantially pointed geometry with an apex comprising a 0.050 to 0.160 inch radius, and a 0.100 to 0.500 inch thickness from the apex to an interface where the super hard material 206 is bonded to the substrate 207. Preferably, the interface is non-planar, which may help distribute loads on the tip 208 across a larger area of the interface. The side wall of the superhard material may form an included angle with a central axis of the tip between 30 to 60 degrees. In asphalt milling applications, the inventors have discovered that an optimal included angle is 45 degrees, whereas in mining applications the inventors have discovered that an optimal included angle is between 35 and 40 degrees. A tip that may be compatible with the present invention is disclosed in U.S. patent application Ser. No. 11/673,634 to Hall and is currently pending.

The wear-resistant tip 208 may be brazed onto the carbide bolster 205 at a braze interface. Braze material used to braze the tip 208 to the bolster 205 may comprise a melting temperature from 700 to 1200 degrees Celsius; preferably the melting temperature is from 800 to 970 degrees Celsius. The braze material may comprise silver, gold, copper nickel, palladium, boron, chromium, silicon, germanium, aluminum, iron, cobalt, manganese, titanium, tin, gallium, vanadium, phosphorus, molybdenum, platinum, or combinations thereof. The braze material may comprise 30 to 62 weight percent palladium, preferable 40 to 50 weight percent palladium. Additionally, the braze material may comprise 30 to 60 weight percent nickel, and 3 to 15 weight percent silicon; preferably the braze material nay comprise 47.2 weight percent nickel, 46.7 weight percent palladium, and 6.1 weight percent silicon. Active cooling during brazing may be critical in some embodiments, since the heat from brazing may leave some residual stress in the bond between the carbide substrate 207 and the super hard material 206. The farther away the super hard material is from the braze interface, the less thermal damage is likely to occur during brazing. Increasing the distance between the brazing interface and the super hard material 206, however, may increase the moment on the carbide substrate 207 and increase stresses at the brazing interface upon impact. The shank assembly 200 may be press fitted into the bolster 205 before or after the tip 208 is brazed onto the bolster 205.

Referring now to FIGS. 5 and 6, the first end 201 of the shank assembly 200 is adapted to expand when a wedge 300 is inserted into the first end 201. The insertion of the wedge 300 into the first end 201 may coincide with insertion of the shank assembly 200 into the cavity 203. The expansion of the first end 201 away from the central axis 403 of the shank assembly 200 may strengthen the attachment between the bolster 205 and the shank assembly 200. In FIG. 6 an embodiment is disclosed in which the wedge 300 is fixed to the carbide bolster 205.

FIG. 7 discloses an embodiment of the invention in which the attachment mechanism is an outwardly tapered surface 701 disposed on the first end 201 of the shank assembly 200. As the shank assembly 200 is inserted into the cavity 203, the tapered surface 701 may attach the bolster 205 and the shank assembly 200 by expanding the first end of the shank assembly 200.

Referring now to FIG. 8, an embodiment is disclosed in which the plurality of prongs 404 are adapted to interlock with the cavity 203 of the carbide bolster 205. In the present embodiment the first end 201 comprises a ledge 801 and the prongs 404 are tapered inward from the ledge 801 toward the central axis 403 of the shank assembly. The prongs 404 may comprise a material having a characteristic of pliability and a spring constant K. The cavity 203 is shaped to receive the plurality of prongs 404 and to interlock with the prongs 404. As the first end 201 of the shank assembly 200 enters the cavity 203 the prongs 404 may flex toward the central axis 403. The prongs may comprise a characteristic of having a flexible resistance against moving toward the central axis 403 defined by its spring constant K. This flexible resistance may generate a force directed away from the central axis 403 and toward the internal surface 405 of the cavity 203. This force may strengthen the connection between the shank assembly 200 and the bolster 205. The shank assembly may be adapted to snap into place as the ledge 801 enters the cavity 203 so that the ledge 801 rests inside the cavity 203. Although the present embodiment discloses an entirely hollow shank assembly 200, in some embodiments the hollow portion of the shank assembly 200 may extend along only a portion of the length 219 of the shank assembly 200.

Referring now to FIGS. 9 and 10, an embodiment is disclosed in which the shank assembly 200 comprises a constricted inner diameter 901 proximate the first end 201. The constricted inner diameter 901 is smaller than the inner diameter 216. A wedge 300 may be inserted into the shank assembly 200 by passing the wedge 300 from the second end 202 towards the first end 201. As the wedge 300 approaches the first end 201, the constricted diameter 901 may cause the wedge 300 to exert a force on the shank assembly 200 that is directed away from the central axis 403 of the shank assembly 200. This force may attach the shank assembly 200 to the bolster 205. The wedge may then still be disposed within the inner diameter 216.

In FIG. 10 an embodiment is disclosed in which the wedge 300 comprises a first set of threads 1001 that correspond to a second set of threads 1002. The second set of thread 1002 is disposed on an inner surface 1003 of the shank assembly 200. As the wedge 300 approaches the first end 201, the wedge 300 may be rotated about the central axis 403 of the shank assembly 200 and the thread sets 1001, 1002 may interlock with one another. This may maintain the wedge 300 inside the inner diameter 216 and proximate the first end 201 and constricted diameter 901 of the shank assembly 200. This feature may also allow the wedge 300 to be removed by rotating the wedge about the central axis 403 in a direction opposite the original direction used to place the wedge 300 proximate the constricted diameter 901. In this embodiment the attachment mechanism 214 is adapted to inducibly release the shank assembly 200 from attachment with the carbide bolster 205.

Referring now to FIGS. 11-13, a split ring 1101 may be disposed in the cavity 203 of the bolster 205 intermediate the first end 201 of the shank assembly 200 and an internal surface 405 of the bolster 205. Attachment of the shank assembly 200 to the bolster 205 may induce stress on the bolster 205. The split ring 1101 may mediate the effect of this stress on the bolster 205. FIG. 11 discloses an embodiment where the first end 201 of the shank assembly 200 comprises ridges 1102 on an outer diameter of the shank assembly 200. The ridges 1102 may help maintain contact between the shank assembly 200 and the split ring 1101. In some embodiments the split ring 1101 may be press fit into the cavity 203 of the bolster 205.

Referring now to FIGS. 14 and 15, the attachment mechanism 214 comprises a plurality of extendable arms 1401 that are each perpendicular to the central axis of the shank assembly 403. Each of the extendable arms 1401 is adapted to interlock with the carbide bolster 205 by extending into a recess 1402 in an internal surface 405 of the cavity 203 of the carbide bolster 205. The extendable arms 1401 may then maintain attachment between the shank assembly 200 and the carbide bolster 205. FIGS. 14 and 15 also disclose embodiments in which translation of an activating mechanism 1403 in a direction 1407 parallel to the central axis 403 of the shank assembly 200 extends the plurality of extendable arms 1401 away from the central axis 403. In FIG. 14 the activating mechanism 1403 is easily removable from the attachment mechanism 214. The activating mechanism comprises a plurality of grooves 1404 adapted to interlock with a plurality of protrusions 1405 disposed on an internal end 1406 of the extendable arms 1401. The activating mechanism 1403 thereby interlocks with at least a portion of at least one of the extendable arms 1401 and thereby maintains the extension of the arm 1401 away from the central axis 403. The shank assembly 200 may be released from the carbide bolster 205 by pulling the activating mechanism 1403 away from the rest of the attachment mechanism 214. In FIG. 15 the activating mechanism 1403 is fixed to the extendable arms 1401.

FIG. 16 discloses an embodiment in which fluid pressure on an expandable bladder 1601 disposed within the shank assembly 200 is adapted to expand the bladder 1601 and thereby extend the plurality of extendable arms 1401 away from the central axis 403 of the shank assembly 200. A funnel 1602 may be used to direct a fluid into the expandable bladder 1601. An elastomeric seal 1603 may be disposed proximate the expandable bladder 1601 and may allow the bladder 1601 to open while maintaining a seal against the bladder 1601. This may prevent the fluid from leaving the bladder 1601. The bladder may be adapted to expand to a predetermined distance, after which the bladder 1601 may no longer expand under the fluid pressure. In some embodiments the fluid may be a lubricant. The expandable bladder 1601 may be adapted to return to its original shape once the fluid pressure is removed from acting on it.

Referring now to FIG. 17, the inducible attachment mechanism 214 comprises a insertable locking mechanism 1701 and also a locking shaft 1702. The locking shaft 1702 is connected to an expanded locking head 1703. The insertable locking mechanism 1701 and locking head 1703 are disposed within the cavity 203 of the carbide bolster 205. The locking shaft 1702 protrudes from the cavity 203 and into an inner diameter 216 of the shank assembly 200. The locking shaft 1702 is disposed proximate a constricted inner diameter 901 proximate the first end 201 of the shank assembly 200. The locking shaft 1702 is adapted for translation in a direction parallel to the central axis 403 of the shank assembly 200. The locking shank may pass through the opening 1710 of the cavity and then the locking mechanism may be inserted afterwards. The locking mechanism may be retained within the cavity through a retention shoulder formed in the cavity, while protruding into the cavity and preventing the locking shank from exiting the opening.

When the first end 201 of the shank assembly 200 is inserted into the cavity 203, the locking head 1703 may be extended away from the constricted inner diameter 901 of the shank assembly 200. The insertable locking mechanism 1701 may be disposed around the locking shaft 1702 and be intermediate the locking head 1703 and the constricted inner diameter 901. The insertable locking mechanism 1701 may comprise an elastomeric material and may be flexible. In some embodiments the insertable locking mechanism may comprise a metal and/or a flexible metal. The insertable locking mechanism may be a split ring, a coiled ring, a rigid ring, segments, balls, or combinations thereof. In embodiments where the insertable locking mechanism 1701 is flexible, the insertable locking mechanism 1701 may comprise a breadth 1704 that is larger than an opening 1710 of the cavity 203. In such embodiments the insertable locking mechanism 1701 may compress to have a smaller breadth 1704 than the available distance 1705. Once the insertable locking mechanism 1701 is past the opening 1710, the insertable locking mechanism 1701 may expand to comprise its original or substantially original breadth 1704.

With both the insertable locking mechanism 1701 and the locking head 1703 past the opening 1710, the first end 201 of the shank assembly 200 may be further inserted into the cavity 203 of the bolster 205. Once the shank assembly 200 is inserted into the cavity 203 to a desired depth, a nut 1706 may be threaded onto an exposed end 1707 of the locking shaft 1702 until the nut 1706 contacts a ledge 1708 proximate the constricted inner diameter 901. This contact and further threading of the nut 1706 on the locking shaft 1702 may cause the locking shaft 1702 to move toward the second end 202 of the shank assembly 200 in a direction parallel to the central axis 403 of the assembly 200. This may also result in moving the locking head 1702 into contact with the insertable locking mechanism 1701, and bringing the insertable locking mechanism 1701 into contact with the internal surface 405 of the bolster 205.

Once the nut is threaded tightly onto the locking shaft 1702, the locking head 1703 and insertable locking mechanism 1701 of the attachment mechanism 214 together are too wide to exit the opening 1710. In some embodiments the contact between the locking head 1703 and the bolster 205 via the insertable locking mechanism 1701 may be sufficient to prevent both rotation of the shank assembly 200 about its central axis 403 and movement of the shank assembly in a direction parallel to its central axis 403. In the present embodiment the attachment mechanism 214 is also adapted to inducibly release the shank assembly 200 from attachment with the carbide bolster 205 by removing the nut 1706 from the locking shaft 1702.

Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention. 

1. A pick, comprising: a carbide bolster disposed intermediate an impact tip and a shank assembly; the impact tip comprising a superhard material bonded to a carbide substrate, the tip being bonded to the bolster opposing a base of the bolster; the shank assembly comprising a central axis, a first end that protrudes into a cavity formed in the base of the bolster, and also an inducible attachment mechanism proximate the first end; and wherein the inducible attachment mechanism is adapted to attach the shank assembly to the carbide bolster and restrict movement of the shank assembly with respect to the carbide bolster.
 2. The pick of claim 1, wherein the inducible attachment mechanism is adapted to restrict rotation of the shank assembly about the central axis when the shank assembly is attached to the carbide bolster.
 3. The pick of claim 1, wherein the inducible attachment mechanism is also adapted to inducibly release the shank assembly from attachment with the carbide bolster.
 4. The pick of claim 1, wherein the inducible attachment mechanism comprises a insertable locking mechanism and also a locking shaft connected to an expanded locking head, the insertable locking mechanism and locking head being disposed within the cavity of the carbide bolster, and the locking shaft protruding from the cavity into an inner diameter of the shank assembly and being adapted for translation in a direction parallel to the central axis of the shank assembly.
 5. The pick of claim 1, wherein the attachment mechanism comprises a wedge disposed within the cavity of the carbide bolster.
 6. The pick of claim 5, wherein the wedge is fixed to the carbide bolster.
 7. The pick of claim 1, wherein the first end of the shank assembly is adapted to expand when a wedge is inserted into the first end.
 8. The pick of claim 1, wherein the first end of the shank assembly comprises a plurality of prongs that are adapted to interlock with the cavity of the carbide bolster.
 9. The pick of claim 1, wherein the attachment mechanism attaches the shank assembly to the carbide bolster by radially expanding at least a portion of the shank assembly.
 10. The pick of claim 1, wherein an internal surface of the cavity comprises outwardly tapered surfaces.
 11. The pick of claim 1, wherein the shank assembly comprises a hollow portion disposed within an inner diameter and also comprises an opening to the hollow portion in a second end of the shank assembly.
 12. The pick of claim 1, wherein the shank assembly comprises a wedge disposed within an inner diameter of the shank assembly.
 13. The pick of claim 12, wherein the wedge comprises a first set of threads that corresponds to a second set of threads disposed on an inner surface of the shank assembly.
 14. The pick of claim 1, wherein a split ring is disposed in the cavity of the bolster intermediate the first end of the shank assembly and an inner surface of the bolster.
 15. The pick of claim 1, wherein the inducible attachment mechanism comprises a plurality of extendable arms that are each perpendicular to a central axis of the shank assembly.
 16. The pick of claim 15, wherein each of the plurality of extendable arms is adapted to interlock with the carbide bolster by extending into a recess disposed in the cavity of the carbide bolster.
 17. The pick of claim 15, wherein fluid pressure on an expandable ring disposed within the shank assembly causes the ring to expand and thereby extend the plurality of extendable arms away from the central axis.
 18. The pick of claim 15, wherein translation of an activating mechanism in a direction parallel to the central axis extends the plurality of extendable arms away from the central axis.
 19. The pick of claim 18, wherein the activating mechanism interlocks with at least a portion of at least one of the plurality of extendable arms and thereby maintains the extension of the arm away from the central axis.
 20. A pick, comprising: a carbide bolster disposed intermediate an impact tip and a shank assembly; the impact tip comprising a superhard material bonded to a carbide substrate, the tip being bonded to the bolster opposing a base of the bolster; the shank assembly comprising a first end that protrudes into a cavity formed in the base of the bolster and also comprising a radial expansion mechanism; wherein the radial expansion mechanism radially expands at least a portion of the shank assembly outward to engage the cavity of the carbide bolster. 